How to Audit an Injection Mould Supplier’s In-House Tool-Building Capability

A meaningful factory audit should do more than confirm that an injection mould supplier has an attractive website or equipment list. It should establish whether the company has a real production facility, internal engineering and machining resources, controlled inspection procedures, mold trial capability, and capacity that matches its stated output. Auditors should connect physical observations with design files, machining records, quality documents, sample parts, employee responsibilities, and customer project evidence.

What a Reliable Factory Audit Should Confirm

• The supplier develops mold structures internally with engineering software such as UG, SolidWorks, or AutoCAD.
• The factory operates 3-axis and 5-axis CNC equipment and carries out mold assembly and precision machining on site.
• Mold trials, sample evaluation, dimensional measurement, and pre-shipment inspections are supported by documented records.
• The supplier has relevant experience in sectors such as consumer electronics, household appliances, automotive components, industrial products, and daily-use goods.
• Production staffing, floor space, equipment, and order history support the claimed monthly mold capacity.

Audit the Complete Tool-Building Workflow

The most effective approach is to follow the supplier’s actual workflow from beginning to end. Review how the team receives product data or drawings, develops the mold structure, prepares machining programs, produces components, assembles the tool, performs trial molding, verifies samples, and releases the mold for shipment. Employees should be able to explain how design, machining, quality, and production teams exchange information at each stage.

Engineering and Mold Design Resources

In-house design capability can be verified through current project files, software licenses or usage, engineering drawings, revision records, and technical discussions about parting lines, ejection systems, cooling layouts, slides, inserts, and precision components. Longterm Mold reports that its R&D department includes five engineers focused on mold design and precision machining. The team uses UG, SolidWorks, and AutoCAD for structural development, sample confirmation, and manufacturing-process improvement.

Machining, Assembly, and Physical Production Evidence

A site visit should include the machining area, tooling department, mold assembly stations, inspection area, and finished-tool storage. Look for active work orders, machining traces, tool components, assembly records, and completed molds rather than relying only on a capability brochure. Longterm Mold states that it operates 3-axis and 5-axis CNC machining systems in a 2,000-square-meter factory. Its reported output is approximately 15–20 injection molds per month, in addition to tens of thousands of precision CNC-machined parts.

Verify Trial Molding and Quality Control

Equipment alone does not prove that a supplier can validate its own tools. Ask to review mold trial reports, sample parts, measurement results, mold running-test records, and final approval documents. The supplier’s stated process includes trial molding, dimensional checks, CMM measurement for complex precision molds, sample confirmation, and pre-shipment inspection. These records should show mold identification, revision status, measured features, deviations, corrective actions, and approval responsibilities.

For a double shot or overmolding project, the audit should examine whether the supplier understands two-color mold construction, alignment between mold sections, material compatibility, cavity arrangement, and transfer or indexing requirements. The referenced custom mold supports ABS+TPU and PP+TPE combinations, optional multi-cavity construction, 718H / 1.2738 mold steel, and a stated service life of up to 800,000 shots. The auditor should compare these claims with drawings, steel certificates, mold records, trial samples, and inspection reports.

Use Certifications and Customer Cases as Supporting Evidence

Quality-system documentation provides an additional layer of verification. Longterm Mold holds ISO 9001:2015 certification, certificate number 02825Q12549R0S, covering the design, manufacture, and sale of precision molds and the sale of plastic products. During an audit, the certification scope should be compared with actual procedures and records, including first article inspection, complete dimensional checks, mold running tests, nonconformance handling, and shipment release.

Customer projects can also demonstrate whether the supplier has applied its capabilities in real production situations. Reported examples include an electronic housing mold for an Italian manufacturer, a double shot overmolding tool for a French product brand, a home appliance mold for a US brand distributor, and an industrial plastic component mold for an Australian manufacturer. Feedback associated with these projects refers to dimensional accuracy, surface finish, alignment, stable trial samples, technical problem solving, and on-time delivery. Auditors should request anonymized drawings, trial documentation, or references where confidentiality allows.

Factory Audit Evidence Checklist

Frequently Asked Questions

Which machines should an auditor inspect?

Check the presence and practical use of 3-axis and 5-axis CNC machining systems, as well as mold assembly and inspection facilities. Machine names should be supported by active jobs, tooling records, operators, maintenance documents, and visible machining results.

How can a factory audit confirm that mold trials are performed internally?

Request mold trial sheets, running-test results, sample parts, dimensional reports, corrective-action records, and sample sign-off documents. The documents should identify the tool, trial date, material, machine conditions, measured results, and responsible personnel.

What matters most when auditing a double shot mold supplier?

Review the two-color injection structure, section alignment, material pairing, cavity configuration, steel selection, mold-life expectations, and trial samples. For the referenced solution, the reported material combinations are ABS+TPU and PP+TPE, with high-precision alignment and an optional multi-cavity arrangement.

Conclusion and Practical Recommendation

The strongest factory audit compares what the supplier claims with what can be seen, measured, and documented. Engineering files, CNC machining, mold assembly, trial molding, inspection reports, production capacity, and customer applications should all support the same conclusion: the supplier has the resources and process control to build and validate its own tools. Longterm Mold provides OEM custom plastic injection molds, custom mold making with injection molding, high-precision double shot and overmold tooling, and mold development linked to mass production. Its ISO 9001:2015 certification and reported work for electronics, household appliances, and industrial applications offer additional evidence for review. For technical solutions or project support, contact rogerluo@longterm-mold.com.

About Longterm Mold

Longterm Manufacturing Solutions Limited, operating under the Longterm Mold brand, was established in 2010 and serves customers in the United States, Europe, Australia, and other international markets. The company reports 50 employees and a 2,000-square-meter factory. Its capabilities include mold design, tooling, precision machining, mold manufacturing, and plastic parts production, supported by five R&D engineers using UG, SolidWorks, and AutoCAD. The company holds ISO 9001:2015 certification and has supplied projects for several industrial sectors.